Ting-Yan Lai, Tyng-Ruey Chuang, and Shin-Cheng Mu. In 2nd Workshop on Type-Driven Development (TyDe), 2017.
Redis is an in-memory data structure store, often used as a database, with a Haskell interface Hedis. Redis is dynamically typed — a key can be discarded and re-associated to a value of a different type, and a command, when fetching a value of a type it does not expect, signals a runtime error. We develop a domain-specific language that, by exploiting Haskell type-level programming techniques including indexed monad, type-level literals and closed type families, keeps track of types of values in the database and statically guarantees that type errors cannot happen for a class of Redis programs.